Painful Bladder Syndrome (PBS) is a condition of bladder hypersensitivity that has proven resistant to diagnosis and treatment. PBS is symptom-based diagnoses similar to other disorders such as fibromyalgia (FM). Proposed etiologies for PBS are many, and include alterations in bladder component structure and function as well as changes in neurological structures related to the bladder. A single type of therapy is unlikely able to treat multiple pathophysiologies. The goal of this grant is to identify clinically relevant subgroups or separate phenotypes within the broader selection of patients that meet the criteria for PBS which would allow for a stratification of patients. In a limited sampling, quantitative sensory testing (QST) of PBS patients has found there to be a suggestion of two different phenotypes based on cutaneous sensory testing. Since one of the groups tests in a fashion that is similar to FM patients the following hypothesis is proposed; Patients with the diagnosis of painful bladder syndrome constitute two or more phenotypes that are distinguished by differential neurophysiological processing of sensory information. Further, these differing phenotypes can be predicted by the presence of absence of co-morbidity fibromyalgia. To test this hypothesis, neurophysiological processing will be assessed psychophysically using standard QST measure and neuropsychological questionnaires and neuroanatomically using an intracerebral bloodflow measure - Continuous Arterial Spin Label functional Magnetic Resonance Imaging (CASL-fMRI), an innovative technology.